add some comments

16/main.go

@@ -209,6 +209,9 @@ func partTwo() {
 	}
 	guesses := guessFields(rules, tickets)
 	var lastRuleSolved int
+	// iterate over the guesses list. on every iteration, only one field has only one rule remaining that's valid
+	// save it off into the rules list, then remove that rule from all fields.
+	// Luckily, we don't need any higher-order elimination logic.
 	for i := 1; i < len(guesses); i++ {
 		for i, g := range guesses {
 			if len(g) == 1 {